1. Field of the Invention
The present invention relates to a bearing adjusting mechanism for use between the cylinder tube and slide table of a rodless cylinder, and more particularly to a bearing adjusting mechanism capable of easily adjusting a bearing in a rodless cylinder.
2. Description of the Related Art
Recently, rodless cylinders have being finding wide use as workpiece feed apparatus in factories or the like. The rodless cylinder takes up a small space and can easily be handled because the length of its displaceable stroke is shorter than conventional cylinders with piston rods and also because it has a highly accurate positioning capability as dust particles are prevented from entering the cylinder unlike conventional cylinders with piston rods.
FIG. 10 of the accompanying drawings shows a rodless cylinder 1 of this type.
As shown in FIG. 10, this rodless cylinder 1 includes a cylinder tube 2, a slide table 3, and a piston (not shown). When supplied with air under pressure through a port (not shown), the piston is displaced to move the slide table 3 linearly back and forth in unison with the piston with respect to the cylinder tube 2. A bearing mechanism is interposed between the slide table 3 and the cylinder tube 2 for allowing the slide table 3 to be displaced smoothly with respect to the cylinder tube 2.
The bearing mechanism shown in FIG. 10 comprises a rail 4 fixed to and extending longitudinally on a side wall of a recess in the cylinder tube 2, and an eccentric roller 5 held in rolling contact with the rail 4. The rolling contact between the rail 4 and the eccentric roller 5 can be adjusted by a bearing adjusting mechanism. The bearing adjusting mechanism comprises a screw 6 threaded in a through hole defined in the slide table 3 and inclined from its upper surface to its lower surface, a rod 7 supported on the screw 6 and holding the eccentric roller 5 thereon for rotation, and a lock nut 8 by which the screw 9 is secured to the slide table 3. The rod 7 is fixed to the screw 6 out of alignment with the central axis of the screw 6. A workpiece 9 to be fed by the rodless cylinder 1 is fixedly mounted on an upper surface of the slide table 3.
When the screw 6 is turned clockwise or counterclockwise by a screwdriver bit or the like, the rod 7 is also turned with the screw 6. Therefore, the eccentric roller 5 is also turned in one of the directions indicated by the arrows for thereby adjusting rolling contact between the rail 4 and the eccentric roller 5.
In the conventional bearing adjusting mechanism, the rolling contact between the rail 4 and the eccentric roller 5 can be adjusted only in the axial direction of the screw 6, i.e., from the upper surface of the slide table 3. After the rolling contact between the rail 4 and the eccentric roller 5 has been adjusted, the workpiece 9 is fastened to the upper surface of the slide table 3. If for some reason the bearing mechanism has to be adjusted again after the workpiece 9 is fastened to the upper surface of the slide table 3, then it is necessary to detach the workpiece 9 from the upper surface of the slide table 3. Such a detachment process and a subsequent process of attaching the workpiece 9 again are quite tedious and time-consuming.
Another problem is that since the direction in which the screw 6 can be accessed for adjustment is limited, the rodless cylinder 1 may have to be removed from another apparatus in which it is incorporated, before the rodless cylinder 1 is serviced for maintenance.